Can I get Minecraft worlds back that have been deleted? If I can how?

Ok so I'm in the process of making a epic build in minecraft but when I went on my minecraft the world was gone! I heard that you can get the world back by going in your.minecraft folder and doing stuff with the saves but I don't want to screw anything up and lose the world for ever can someone please Help!

If they are completely removed, then there's no way.
If you have a backup of the worlds,
1: click start -> run -> write %appdata% press enter
2: goto.minecraft, then saves and put them there

You can check your bin( don't know the right term ) it might be there, sometimes my computer deletes things and I just simply pull them back to my computer from the bin.
*If your save is there just pull it to your destop.
*then go to start > run > %appdata% > .minecraft > saves
*drop the folder in and you should be ready to go.
If it isn't even in the bin and you are sure that you have checked everywhere than your world is gone, sorry.